Liquid detergents are often considered to be more convenient to employ than dry powdered or particulate products. They are readily measurable, rapidly dissolved in the wash water, capable of being easily applied in concentrated solutions or dispersions to soiled areas on garments to be laundered and are non-dusting. Additionally, the liquid detergents may include materials that could not stand drying operations without deterioration, which materials are often desirably employed in the manufacture of particulate detergent products.
In particular, liquid detergent ingredients such as enzymes, bleach (e.g. hydrogen peroxide) and alkalizing agents contribute greatly to the removal of stains and soils. Multiple enzymes are typically used in detergent formulations to deliver a wide range of stain removal. These enzymes include, but are not limited to proteases (for stains/soils containing proteins such as dairy or grass), lipases (for stains/soils containing lipids such as butter or make-up), amylases (for stains/soils containing starches such as potatoes or gravy), and cellulases (for stains/soils containing cellulose such as fruits or vegetables). Meanwhile, bleaches work effectively against non-fatty stains such as red wine or coffee. Higher alkalinity can be provided by sodium carbonate or percarbonate, which helps to counteract water hardness and increase detergency.
However, most laundry detergents do not deliver all three mechanisms of stain removal due to incompatibility and interactions of the components that deliver these chemistries, particularly because current detergent systems are water based, which presents a challenge in stabilizing such a system. For example, enzymes that are typically only stable at a pH level of 6-9 can be unstable in a large presence of water. Bleaches, based on sodium percarbonates or hydrogen peroxide, are also unstable in aqueous environments at an alkaline pH level.
One of the approaches to deliver all of the cleaning ingredients together is to develop a pourable and substantially anhydrous paste or slurry system, which includes suspended percarbonate and/or carbonate salts and enzymes. The substantially anhydrous system is beneficial because the sodium percarbonate and enzymes would be stable in the absence of water, and they remain inactive until the system is in contact with a wash liquor. Furthermore, the incorporation of these salts in a stable anhydrous composition also provides an option to meter and package the composition in a dissolvable pouch or container. A dosed and contained detergent composition that requires minimal handling is highly desirable by consumers.
Various attempts are well known in the prior art to produce stable anhydrous detergents. For example, U.S. Pat. No. 4,264,466 to Carleton et al. teaches liquid laundry detergents that contain a chain structure type clay that is selected from attapulgite, sepiolite and palygorskite clays as a suspending agent.
Another example is U.S. Pat. No. 6,656,901 to Moorfield et al., which teaches a fabric care composition comprising an organophilic clay, a functionalized oil and water to provide softness benefits to fabric.
U.S. Pat. No. 4,846,992 to Fonsny teaches a non-aqueous liquid laundry detergent composition comprising a suspension of builder salt in a liquid nonionic surfactant. The stability of the composition is improved by the addition of small amounts of organophilic-modified clay. The stability is further enhanced by reducing the solid particulate matter to a particle size below about 15 microns.
U.S. Pat. No. 4,316,812 to Hancock et al. teaches a liquid detergent composition comprising a dispersion of solids that includes one or more builders and bleach. The solids have an average particle diameter of less than 10 microns. Suitable inorganic builders include phosphates, tetrasodium pyrophosphate, sodium hexametaphosphate and, preferably, sodium tripolyphosphate, carbonates (e.g. sodium carbonate), sodium bicarbonate and sodium sesquicarbonate, clays (e.g. kaolin, montmorillonites and sodium bentonite), sodium borate, sodium citrate sodium meta-silicate and nitrilotriacetic acid.
U.S. Pat. No. 4,661,280 to Ouhadi et al. teaches a liquid heavy duty laundry detergent composition comprising a suspension of builder salt in a liquid nonionic surfactant, and at least one additional suspension stabilizing agent that is selected from the following: quaternary ammonium compounds, phosphoric esters, modified clays and mixtures thereof.
U.S. Pat. No. 5,176,713 to Dixit et al. teaches a non-aqueous liquid laundry detergent composition comprising a builder salt suspension in a liquid nonionic surfactant. The composition is stabilized against phase separation by the addition of small amounts of low density fillers, such as hollow plastic or glass microspheres.
The above references teach various means to stabilize liquid detergent ingredients with the addition of fillers, builders and/or salts. However, there remains a need to formulate a stable liquid anhydrous detergent composition with a high proportion of dispersed solid materials.